I once worked with someone who got both of us a pay rise by vocally complaining to a senior manager.

He specifically used the "Squeaky wheel gets the oil" metaphor to describe what he'd done and why it worked.

The "oil" is money.

I think you're gravely mistaken about that. I have absolutely heard people quoting this to justify demands of rewards, whether monetary or status; an even pithier version is 'if you don't ask, you don't get.'

I thought oil was money in this metaphor.